Ph.D Thesis

Ph.D StudentCohen-Elias Doron
SubjectUltra Small Fast Indium Phosphide Based Transistors
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Dan Ritter
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Increasing the operation frequency of electronic circuits is an ongoing and demanding goal. For example: in communication systems increasing the frequency range increases the amount of transmitted information. In circuits used in computers increasing of the clock rate enhances the speed of computation. Raising the clock rate of analog to digital converters improves sampling and resolution of the signals. Another important example for the need for high frequency circuits is terahertz imaging systems which enable discovering hidden objects.

Among the various transistor types, the transistors made of the indium phosphide material system are excellent candidates for achieving ultra high cutoff frequencies. The indium phosphide material system includes all semiconductors that can be grown epitaxially on an indium phosphide substrate. The high electron velocity in this material system made it possible to prepare the fastest transistors available to date.

This research thesis describes a study of bipolar transistors made of the indium phosphide material system. Bipolar transistors are competing with field effect transistors made of the same material system for record speed performance. In order to increase the speed of operation of indium phosphide based bipolar transistors their dimensions need to be scaled down to the nanometer range. However, scaling down the dimensions without reducing contact resistivity degrades the performance instead of enhancing it. An obvious solution is to reduce contact resistivity. Reducing contact resistivity is extremely challenging, although technologically feasible. This thesis presents an alternative solution: novel transistors structures that can enhance the frequency performance of the bipolar transistor.

Three new device structures are presented in this thesis. One structure is a significant technological modification of the conventional structure. The two other structures are more radical modifications of the conventional structure.